Add "SnapshotCreated" event for snapshot-controller

[rexagod]

Fixes: #522

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind api-change
/kind bug
/kind cleanup
/kind design
/kind documentation
/kind failing-test

/kind feature

/kind flake

What this PR does / why we need it:
Adds SnapshotCreated and SnapshotReady events to snapshot-controller.

Which issue(s) this PR fixes:

Fixes #522

Special notes for your reviewer: This is my first PR here, and I hope this is the expected change, but if not, please let me know and I'll look into it right away. Thanks!

Does this PR introduce a user-facing change?:

Introduced "SnapshotCreated" and "SnapshotReady" events.

[k8s-ci-robot]

Welcome @rexagod!

It looks like this is your first PR to kubernetes-csi/external-snapshotter 🎉. Please refer to our pull request process documentation to help your PR have a smooth ride to approval.

You will be prompted by a bot to use commands during the review process. Do not be afraid to follow the prompts! It is okay to experiment. Here is the bot commands documentation.

You can also check if kubernetes-csi/external-snapshotter has its own contribution guidelines.

You may want to refer to our testing guide if you run into trouble with your tests not passing.

If you are having difficulty getting your pull request seen, please follow the recommended escalation practices. Also, for tips and tricks in the contribution process you may want to read the Kubernetes contributor cheat sheet. We want to make sure your contribution gets all the attention it needs!

Thank you, and welcome to Kubernetes. 😃

[k8s-ci-robot]

Hi @rexagod. Thanks for your PR.

I'm waiting for a kubernetes-csi member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[xing-yang]

At this point, the VolumeSnapshotContent is just created. The CSI snapshotter sidecar will call the CSI driver to create a snapshot, but we don't know whether it is completed yet.

In updateSnapshotStatus (https://github.com/kubernetes-csi/external-snapshotter/blob/v4.1.1/pkg/common-controller/snapshot_controller.go#L1072), we know whether snapshot is created successfully.

Add a snapshot is created successfully event in this if block:
https://github.com/kubernetes-csi/external-snapshotter/blob/v4.1.1/pkg/common-controller/snapshot_controller.go#L1155

Add a snapshot is ready to use event in this if block:
https://github.com/kubernetes-csi/external-snapshotter/blob/v4.1.1/pkg/common-controller/snapshot_controller.go#L1162

[rexagod]

Thank you for the detailed explaination, Xing!

[xing-yang]

Can you change this from "/kind bug" to "/kind feature"?

[xing-yang]

/ok-to-test

[xing-yang]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: rexagod, xing-yang

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [xing-yang]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment